Meanwhile, Senate President Therese Murray, who has been quiet on the proposal, said after a three-hour Democratic caucus that the heckling Obama received during a congressional address Wednesday might have influenced state legislators to support the temporary appointment, motivated by hopes for federal health care legislation.

Still, Senate and House members said the levels of support for the proposal remained unclear, despite consistent pressure from Washington Democrats that increased yesterday with Obama asking supporters to call their legislators and lobby for the bill’s passage.

Obama’s political operation, Organizing for America, called the empty Massachusetts seat, which would give Senate Democrats a 60th seat and probably prevent a Republican filibuster, “a needed vote in favor of real health reform.’’

“We need to make sure that Governor Patrick can appoint an interim senator until a special election can be held,’’ the group said.

Republicans said Obama’s involvement, after weeks of public neutrality, is proof that Democrats are motivated by politics rather than good government.

“I think the e-mail confirms that Democrats are changing the election law for political purposes,’’ said Tarah Donoghue, spokeswoman for the state GOP. “I think it’s a plea to preserve the filibuster-proof majority in the Senate and rush through the health care reform bill.’’

A new poll released yesterday shows declining support for an interim senator law, with respondents roughly split.

Legislative leaders continue to say publicly they are digesting input around the law change, which Kennedy requested in a letter delivered to Patrick and legislative leaders a week before he died.

Murray said there was “no resolution’’ after yesterday’s meeting, but pointed to US Representative Joseph Wilson’s shouted accusation that Obama had lied about details of the federal health care legislation as a pivot point.

“There’s a lot of outrage about that and the way he was treated, which I think might have moved some people to the other side,’’ Murray told reporters.

Members said Murray and House Speaker Robert DeLeo have not polled members.